Stripping Knife

ABSTRACT

[Problems] To ensure the sharpness of a stripping knife whereby a part of a living tissue is incised and stripped while preventing a cut along the thickness direction. 
     [Means for Solving Problems] A stripping knife (A) having a plate-shaped blade ( 3 ) having an edge ( 1 ) around the periphery, a shank ( 5 ) connected to the blade ( 3 ), and a handle ( 7 ) holding the shank ( 5 ) in the integrated state, wherein the blade ( 3 ) is composed of the edge ( 1 ) formed at the front end and a guide face ( 2 ) which is formed between the edge ( 1 ) and the front face ( 3   b ) of the connected plate constituting the blade ( 3 ) and brought into contact with the surface ( 13 ) of the remaining tissue.

TECHNICAL FIELD

The present invention relates to a stripping knife used for stripping apart of tissue from a living body.

BACKGROUND ART

There is a surgery that involves thinly stripping a part of a livingtissue. Such surgery includes a case where tissue is required to beremoved from a living body or where partially stripped tissue is notremoved and allowed to remain clinging to the living body after surgery.In both the cases, it is preferable that the stripped surface of tissueis as smooth as possible. In particular, it is preferable that astripped piece is uniform in thickness.

When a tissue part to be stripped is muscle or skin, a surgical knife orsimilar, which is comparatively easy to manipulate can be used. However,in the case of sites such as a blood vessel or eyeball sclera, the areaof tissue to be stripped is small and, therefore, a knife with a verysmall blade is used.

It is preferable that a knife for stripping a part of tissue cutsharply. However, in view of the specialty of stripping tissue sothinly, a problem is raised; that is, a too sharp knife may cut tissuein the depth direction, so it may be required to correct manipulation ateach time, which may result in a roughness of the stripped surface,thereby making it difficult to obtain a smooth surface.

For example, in surgery for glaucoma, Schlemm's canal is incised andaqueous humor is discharged, thereby reducing ocular tension. Schlemm'scanal is located near and under the scleral spur. Accordingly, thesurgery is performed as follows: the sclera is incised into asubstantially rectangular shape except for the side located next to thecornea. Then the sclera is stripped from the incised portion toward theremaining side, thereby forming a valve or flap from the strippedsclera, thus leaving the sclera in the living body.

When stripping sclera as described above, a knife generally called “agolf knife” is used. A golf knife includes: a substantially linear shankattached to a handle; and a plate-shaped blade disposed at the leadingend of the shank and has an axis that inclines with respect to the axisof the flat surface of the shank. This knife therefore has a shapesimilar to a golf club, in a plan view.

The cutting edge of the golf knife is formed at a periphery of theplate-shaped blade. Using this cutting edge, the sclera is incised andthe incised site is stripped. This cutting edge has a sharp leading endformed by grinding the periphery of the blade in the direction of thethickness of the blade. Therefore, the cutting edge has a cross-sectionof triangular in which a sharp leading end is located substantially inthe middle in the direction of the thickness from the surfaces of aplate forming the blade.

Sclera has a relatively high strength. Sclera may be stripped by movingthe knife sideways in alternate directions. This may result inroughening of the surface of the sclera stripped by the golf knife.Therefore, the golf knife used for stripping sclera is generally buffedor suchlike in order to blunt its edge forcibly.

In cataract surgery, the cornea is incised and a lens is inserted.Generally, the knife used to incise the cornea requires great sharpness(see Patent Document 1, for example).

Heart surgery for removing fat from around a blood vessel also uses agolf knife as described above (in heart surgery, it is generally calleda “hockey knife”). In this type of surgery, using the cutting edge ofthe golf knife, fat adhering to a blood vessel is stripped and collectedtoward one side.

Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No.2005-334054

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Surgery in which sclera is incised or stripped using a golf knife theedge of which has been forcibly blunted has a problem that extra forcemay be applied to cut the sclera and it is required to manipulate thegolf knife finely. This problem is common to the knife when used forstripping tissue in other sites, for example, blood vessel walls.

An object of the present invention is to provide a stripping knife thatis sharp and capable of preventing over-cutting in the thicknessdirection of the tissue.

Means for Solving the Problem

A stripping knife according to the present invention which is directedto solve the foregoing problems is a stripping knife used for strippingtissue, including: a plate-shaped blade having a cutting edge formed ata periphery of the blade; a shank continuously formed from the blade;and a handle holding the shank in an integral state. In this strippingknife, the blade includes the cutting edge formed at the leading end ofthe blade and a guide face which is formed between the cutting edge anda surface of the plate formed continuously from the cutting edge to formthe blade contacts with a surface of the remaining tissue. In addition,the blade may have an axis inclining to the axis of the shank. A guideface may be formed on each side of the blade.

EFFECT OF THE INVENTION

In the stripping knife according to the present invention, when asurgeon incises tissue while gripping and manipulating the handle andstripping an incised site from a living body, one of the guide faces ofthe blade comes into contact with the surface of the remaining tissue,thereby determining the direction in which the stripping knife ismanipulated. When one of the guide faces is brought into contact withthe surface of the remaining tissue, the stripping knife enables theedge of the leading end of the cutting edge to be positioned higher thana line extending from this guide face. This prevents the blade fromcutting into the living tissue in the depth direction despite thesharpness of the blade. This prevents the blade from roughening thesurface of stripped tissue, thus ensuring that the stripped surface ofthe tissue is smooth. Even in heart surgery, the stripping knife isprevented from cutting into a living body in the depth direction andpenetrating a blood vessel.

In addition, the axis of the blade inclines with respect to the axis ofthe shank. This makes it possible to orient the axis of the blade in adirection opposite to the direction in which a surgeon naturally gripsthe knife (when the surgeon is located upstream of the direction inwhich sclera is incised, especially in the case of sclera); in otherwords, the axis of the blade inclines in a direction canceling theinclination of the handle and shank with respect to the surgery site.Accordingly, unlike a case when the axis of the blade coincides withthat of the shank, a surgeon does not have to be in an uncomfortableposition in order to orient the handle and shank in the direction inwhich tissue is to be incised. Thus, the direction of forward movementof the blade and the direction in which tissue is to be incisedcoincide, so that a surgeon is able to perform surgery easily in aposition natural to him or her.

Additionally, guide faces are formed on both sides of the blade.Accordingly, both sides of the blade can be used, and thus even thoughthe axis of the blade incline, smooth surgery is enabled without theneed for specifically orienting the direction of forward movement of theblade.

In particular, this makes it possible to improve the sharpness of thecutting edge, thus eliminating an extra force when the stripping knifeis manipulated, and thereby enhancing responsiveness. This ensuressmooth surgery for stripping a part of tissue from a living body.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view of a stripping knife according to a firstembodiment.

FIG. 2 is an enlarged view of a blade.

FIG. 3 is an enlarged view of a cross-section along axis 3 a shown inFIG. 2.

FIG. 4 is an explanatory view of stripping tissue.

EXPLANATIONS OF REFERENCE NUMERALS

-   -   A Stripping knife    -   1 Cutting edge    -   2 Guide face    -   3 Blade    -   3 a Axis    -   3 b Surface    -   5 Shank    -   5 a Axis    -   7 Handle    -   10 Tissue    -   11 Stripped tissue    -   12 Strip point    -   13 Stripped tissue surface

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter will be described the preferred embodiment of a strippingknife according to the present invention. The stripping knife accordingto the present invention is used for incising a part of tissue on aliving body and stripping the incised tissue from the living body. Thisknife is designed to ensure a smooth stripped surface without degradingsharpness.

The stripping knife according to an embodiment the present inventionincludes: a plate-shaped blade having a cutting edge formed around itsperiphery; a shank; and a handle holding the shank in the integratedstate. In the present invention, the blade and shank are not limited toa flat shape. In particular, it is preferable that the blade has theoptimum shape for the type of tissue to be stripped.

First Embodiment

The configuration of a stripping knife according to a first embodimentwill be described with reference to the drawings. FIG. 1 is a front viewof a stripping knife according to the present embodiment. FIG. 2 is anenlarged view of a blade. FIG. 3 is an enlarged view of a cross-sectionalong the axis of the blade shown in FIG. 2. FIG. 4 is an explanatoryview of stripping tissue.

The stripping knife A has the same flat shape as that of a knifegenerally called “a golf knife”, which is widely used to incise a partof the sclera in glaucoma treatment and to strip the incised sclera.

The stripping knife A includes: a blade 3 having a cutting edge 1 formedat a periphery thereof and having an edge at the leading end and guidefaces 2 formed continuously from the cutting edge 1 on both sides of theblade 3; a shank 5 formed continuously from the blade 3; and a handle 7holding the shank in an integral state.

Particularly, in the golf knife shown in FIG. 1, the axis 5 a of theshank 5 coincides with that of the handle 7. However, the blade 3 islocated at the leading end of the shank 5 and has an axis 3 a incliningwith respect to the axis 5 a of the shank 5. The blade 3 has the cuttingedge 1 and guide faces 2 around the axis 3 a. Therefore, the blade 3 andthe shank 5 together form a shape that looks like a golf club in a planview. Since the blade 3 has the axis 3 a inclining with respect to theaxis 5 a of the shank 5, the following positional relation can beestablished: (especially, when a surgeon is located upstream in thedirection in which he or she incises sclera) the axis 3 a of the blade 3inclines in the direction opposite to the direction in which the surgeonnaturally grips the knife (the axis of the blade 3 inclines in adirection to cancel the inclination of the handle 7 and the axis 5 a ofthe shank 5 with respect to the direction in which an surgery site isincised). This prevents such a situation that a surgeon has to be in anuncomfortable position to orient the handle 7 and shank 5 in thedirection in which the surgery site is to be incised, as in the casewhen the blade 3 has the same axis 5 a of the shank 5. Thus, a surgeoncan perform an operation in a natural position since the direction inwhich the blade 3 moves forward and the direction in which the area tobe incised coincide. It is preferable that the axis 3 a of the blade 3inclines at an angle of approximately 30° to 40°.

In addition, it is preferable that the curvature radius R of the cuttingedge 1 of the periphery of the blade 3 is approximately from 0.45 to 0.7mm, although it depends on the width of the tissue to be stripped. If Ris less than 0.45 mm, the blade 3 may tend to move forward whilerotating slightly (to the right or left) around the axis 5 a, or maytend to be stuck into tissue. Accordingly, the guide faces cannot exertthere effect even when provided, resulting in a non-uniform strippedsurface. If R is greater than 0.7 mm, on the other hand, it is difficultto cope with a small stripping area and degrades the knife'soperability.

The blade 3 and the shank 5 are integrally formed of metal. The thusintegrated shank 5 is then held in the integrated state with the handle7. The structure in which the shank 5 is integrated with the handle 7 isnot limited to this. When the handle 7 is made of a synthetic resin, theshank 5 may be integrated with the handle 7 by its beinginsertion-molded into the handle 7, driven into the handle 7, or byadhesion. When the handle 7 is made of metal, the shank 5 and the handle7 may be integrated by providing a chuck at the leading end of thehandle 7 and holding the shank 5 by means of this chuck. In addition,regardless of whether the handle 7 is made of resin or metal, the shank5 may be integrated with the handle 7 by being screwed into the handle7.

The handle 7, which is gripped by a doctor for manipulation of thestripping knife, is made of synthetic resin or metal, has a shape thatensures a secure grip, and also has a structure that securely holds theshank 5 in the integrated state. In other words, as long as the handle 7holds the shank 5 securely and ensures a secure grip of the handleduring manipulation of the knife, the material and shape of the handle 7are not limited. Further, the shank 5 and handle 7 need not be connecteddirectly. A holder for holding the shank 5 may be provided and connectedto the handle 7 that allows connection with the holder.

The blade 3 has a plate-like shape. However, the shank 5 is not limitedto a plate- or rod-like shape but may have an optimal cross-sectionalshape corresponding to the holding structure of the handle 7. When boththe blade 3 and shank 5 have a plate-like shape, blanks formed by cutout by press cutting a metal plate may be used as materials tomanufacture the blade and shank. When the shank 5 is a round or squarerod, the blade 3 may be manufactured by pressing this round or squarerod (which is a component of the shank 5 and yet is also used asmaterial for the blade) into a plate shape.

Materials for the blade 3 and shank 5 are not limited to these, andcarbon tool or stainless steel may be used. However, since it is notpreferable that the blade 3 or shank 5 rust during distribution,austenite stainless steel free from rust is preferred. It is alsopreferable that the leading end of the blade 3 have a round shape in aplan view, but it may also be polygonal, such as triangular or square.

Additionally, the cutting edge 1 has to be sufficiently sharp to stripliving tissue. Therefore, if a metal material expected to be hardened byheat treatment is used, before or after the formation of the cuttingedge 1, the metal needs to be hardened by heat treatment at an optimumtemperature for the used material. If austenite stainless steel is used,which is not expected to be hardened by heat treatment, it is requiredto impart a required hardness to the austenite stainless steel byhardening through cold processing. In particular, a material obtained bystretching an austenite texture into the form of fibers by cold-drawingaustenite stainless steel wire is preferred because it exhibits greathardness and bending strength.

Each of the guide faces 2 is defined between the cutting edge 1 and thesurfaces 3 b of the plate-like portion of the blade 3. The function ofthe guide faces 2 is to guide the stripping knife A in the direction inwhich the stripping knife A is manipulated (the direction of movement ofthe stripping knife A), while keeping contacting with the surface of thetissue left in the living body after partial stripping. In the presentembodiment, the guide faces 2 are formed on both sides of the blade 3.Additionally, inclination angles of the respective guide faces 2 on boththe sides of the blade 3 with respect to the surface 3 b of theplate-like portions of the blade 3 are substantially equal. In such aconfiguration, even when the axis 3 a of the blade 3 inclines, thesurgeon can reverse the blade 3 to reverse the inclining direction ofthe blade 3 and still used. This does not restrict the direction offorward movement of the blade 3 to a fixed range, thus enabling smoothsurgery.

Accordingly, each of the guide faces 2 are configured to have an angleand a dimension (the distance from its boundary with the cutting edge 1to the surface 3 b of the blade 3) so as to ensure a stable positionwhen a doctor manipulates the stripping knife A. In particular, theangle α (see FIG. 3( b)) of each guide face 2 is twice the angle of asurgeon manipulating the stripping knife A with respect to tissue to bestripped, that is, the angle of the stripping knife A with respect totissue to be stripped.

In the present embodiment, the angle of the stripping knife with respectto the tissue when sclera is the tissue to be stripped falls within therange from 15° to 20° as a result of, for example, the inventor'sexperiences of actually stripping a sample (the eye balls of pigs, forexample) or investigations through interviews. Taking into account thisrange of angle and the elasticity of the tissue to be removed, the angleα of each guide face 2 of the stripping knife A is set within the rangefrom 28° to 40°. It is preferable each guide face 2 be sufficientlywider than the cutting edge 1, although it depending on the thickness ofthe blade 3. In the present invention, the thickness of the blade 3 is0.3 mm, and the widths of the cutting edge 1 and each guide face 2 alongthe axis 3 a are 0.08 mm and 0.36 mm respectively. Accordingly, in thepresent embodiment, the ratio of the cutting edge 1 to each guide face 2is 1:4.5; however, these values are not limited and may be selectedaccording to the thickness of the blade 3 (approximately 1:3 to 7 times,for example).

The angle β of the cutting edge 1 is greater than the angle α of eachguide face 2 and is sufficiently sharp to strip tissue. In the presentembodiment, it is assumed that the tissue to be stripped is sclera, andthe angle at which the stripping knife is able to strip the sclerasmoothly has been tested using samples described above. As a result, theangle β is set within the range from 40° to 50°. In addition, when thethickness of the blade 3 is about 0.3 mm, it is preferable that thethickness of the rear end of the cutting edge 1 (the boundary of thecutting edge 1 with each guide face 2) is from 50 to 90 μM. Here, thelower limit 50 μm is used when the angles α and β are 28° and 40°respectively and the ratio of the cutting edge 1 to the guide face 2 is1:7. And the upper limit 90 μm is used when the angles α and β are 40°and 50° respectively and the ratio of the cutting edge 1 to the guideface 2 is 1:3.

Since the cutting edge 1 and each guide face 2 that have such angles arecontinuously formed, the leading end of the cutting edge 1 when a tissue10 is stripped is located higher than a line extending from the guideface 2, as shown in FIG. 4.

Accordingly, when a tissue 10 is incised vertically with the cuttingedge 1 or with another knife, thereby defining a incision portion in thethickness direction of the tissue, and then the stripping knife A ismoved forward in the direction of arrow (a) from the incision portionwhile the stripped tissue 11 is gripped upwardly with tweezers, thestrip point 12 at which the tissue 10 is being stripped is alwayslocated higher than a line extending from the guide face 2 being used.This prevents the stripping knife from cutting the tissue continuouslyin the depth direction. Additionally, each guide face is setsufficiently wider than the cutting edge 1, thus stabilizing the forwardmovement of the edges.

Accordingly, when the cutting edge 1 cuts the tissue 10 in the depthdirection in the course of stripping the tissue 10, a surgeon does nothave to change the position of the stripping knife A in such a mannerthat the cutting edge 1 faces upward. This prevents the stripped tissuesurface 13 from roughening as a result of changes in the position of thestripping knife A, and makes it possible to obtain a nearly smoothstripped tissue surface 13.

The foregoing description is an example when the stripping knife A isused for stripping sclera in ophthalmic surgery. However, the presentinvention is not limited to use with sclera, but may also be effectivelyused for stripping other tissues such as fat adhering to a blood vessel.Additionally, the present invention is not limited in coating the bladesurfaces with silicon. However, when, for example, sharpness isrequired, the sharpness may be improved by coating a part of the blade(the side that is not usually used for stripping in the blade, forexample) or by coating the entire blade.

INDUSTRIAL APPLICABILITY

A stripping knife according to an embodiment of the present invention isable to ensure the smoothness of the stripped surface of the tissue apart of which is stripped, and is effective for use in stripping tissuein ophthalmic and other surgery.

1. A stripping knife used for stripping tissue, comprising: aplate-shaped blade having a cutting edge formed at a periphery of theblade; a shank formed continuously from the blade; and a handle holdingthe shank in an integrated state, wherein the blade includes the cuttingedge formed at the leading end of the blade and a guide face which isformed between the cutting edge and a surface of the plate formedcontinuously from the cutting edge to form the blade and contacts with asurface of a remaining tissue.
 2. A stripping knife according to claim1, wherein the blade has an axis inclining with respect to the axis ofthe shank.
 3. A stripping knife according claim 1, wherein the guideface is formed on each side of the blade.
 4. A stripping knife accordingclaim 2, wherein the guide face is formed on each side of the blade.